I've got another question about relativity. The speed of light is the same for all observers, right? So let's say there's a planet that's exactly one light year away and not moving relative to Earth. Some weird freaky alien sends a beam of light from there towards Earth. There are two people standing next to each other on Earth when this happens. I think it makes sense to talk about the beam being emitted at the same time as the people standing next to each other because the two locations they are not moving relative to each other. Or at least the events are simultaneous for anyone stationary relative to Earth or this other planet.

And because the speed of light is the same for all observers, that basically means that you can't try to outrun a light beam. (Well, you can try but you'll fail.) So both of these people will experience exactly a year before the light beam reaches them (we'll assume that they only move in a straight line towards or away from the light beam.) It's a light year away from the people and it will travel at one light year per year towards them. It will reach them in a year whatever they do. Right? If one of them starts to move away from the light beam then presumably there must be some relativistic effect to sort this out (time going at a different speed or something).

But one of these people moves away from the light beam at a really high speed and then back again rejoining the other person that has just stood still. And as you all know, this can mean that the two people's watches can read different times from each other. So the person that travelled is now a minute behind the one who stood still. And then the light beam reaches the spot where they are standing. But now how can they both have experienced exactly a year when one has experienced a minute less than the other?

Gavin Chipper wrote:I've got another question about relativity. The speed of light is the same for all observers, right? So let's say there's a planet that's exactly one light year away and not moving relative to Earth. Some weird freaky alien sends a beam of light from there towards Earth. There are two people standing next to each other on Earth when this happens. I think it makes sense to talk about the beam being emitted at the same time as the people standing next to each other because the two locations they are not moving relative to each other. Or at least the events are simultaneous for anyone stationary relative to Earth or this other planet.

And because the speed of light is the same for all observers, that basically means that you can't try to outrun a light beam. (Well, you can try but you'll fail.) So both of these people will experience exactly a year before the light beam reaches them (we'll assume that they only move in a straight line towards or away from the light beam.) It's a light year away from the people and it will travel at one light year per year towards them. It will reach them in a year whatever they do. Right? If one of them starts to move away from the light beam then presumably there must be some relativistic effect to sort this out (time going at a different speed or something).

But one of these people moves away from the light beam at a really high speed and then back again rejoining the other person that has just stood still. And as you all know, this can mean that the two people's watches can read different times from each other. So the person that travelled is now a minute behind the one who stood still. And then the light beam reaches the spot where they are standing. But now how can they both have experienced exactly a year when one has experienced a minute less than the other?

To the travelling person the light has travelled a shorter distance due to the phenomenon of length contraction when two things are moving relative to one another. She will observe that the light has travelled 0.999998 of a light year due to the alien and her earth colleague being (from her perspective) closer than a light year apart during the times she was moving.

At least that's what I understand. You'd be well advised to get confirmation from a genuine physicist.

Gavin Chipper wrote:I've got another question about relativity. The speed of light is the same for all observers, right? So let's say there's a planet that's exactly one light year away and not moving relative to Earth. Some weird freaky alien sends a beam of light from there towards Earth. There are two people standing next to each other on Earth when this happens. I think it makes sense to talk about the beam being emitted at the same time as the people standing next to each other because the two locations they are not moving relative to each other. Or at least the events are simultaneous for anyone stationary relative to Earth or this other planet.

And because the speed of light is the same for all observers, that basically means that you can't try to outrun a light beam. (Well, you can try but you'll fail.) So both of these people will experience exactly a year before the light beam reaches them (we'll assume that they only move in a straight line towards or away from the light beam.) It's a light year away from the people and it will travel at one light year per year towards them. It will reach them in a year whatever they do. Right? If one of them starts to move away from the light beam then presumably there must be some relativistic effect to sort this out (time going at a different speed or something).

But one of these people moves away from the light beam at a really high speed and then back again rejoining the other person that has just stood still. And as you all know, this can mean that the two people's watches can read different times from each other. So the person that travelled is now a minute behind the one who stood still. And then the light beam reaches the spot where they are standing. But now how can they both have experienced exactly a year when one has experienced a minute less than the other?

To the travelling person the light has travelled a shorter distance due to the phenomenon of length contraction when two things are moving relative to one another. She will observe that the light has travelled 0.999998 of a light year due to the alien and her earth colleague being (from her perspective) closer than a light year apart during the times she was moving.

At least that's what I understand. You'd be well advised to get confirmation from a genuine physicist.

Thanks for the answer, but I'm not sure I'm convinced. This person would have been stationary when the light set off on its journey and when it arrived and the light would have travelled a measurable light year according to this person.

Gavin Chipper wrote:I've got another question about relativity. The speed of light is the same for all observers, right? So let's say there's a planet that's exactly one light year away and not moving relative to Earth. Some weird freaky alien sends a beam of light from there towards Earth. There are two people standing next to each other on Earth when this happens. I think it makes sense to talk about the beam being emitted at the same time as the people standing next to each other because the two locations they are not moving relative to each other. Or at least the events are simultaneous for anyone stationary relative to Earth or this other planet.

And because the speed of light is the same for all observers, that basically means that you can't try to outrun a light beam. (Well, you can try but you'll fail.) So both of these people will experience exactly a year before the light beam reaches them (we'll assume that they only move in a straight line towards or away from the light beam.) It's a light year away from the people and it will travel at one light year per year towards them. It will reach them in a year whatever they do. Right? If one of them starts to move away from the light beam then presumably there must be some relativistic effect to sort this out (time going at a different speed or something).

But one of these people moves away from the light beam at a really high speed and then back again rejoining the other person that has just stood still. And as you all know, this can mean that the two people's watches can read different times from each other. So the person that travelled is now a minute behind the one who stood still. And then the light beam reaches the spot where they are standing. But now how can they both have experienced exactly a year when one has experienced a minute less than the other?

To the travelling person the light has travelled a shorter distance due to the phenomenon of length contraction when two things are moving relative to one another. She will observe that the light has travelled 0.999998 of a light year due to the alien and her earth colleague being (from her perspective) closer than a light year apart during the times she was moving.

At least that's what I understand. You'd be well advised to get confirmation from a genuine physicist.

Thanks for the answer, but I'm not sure I'm convinced. This person would have been stationary when the light set off on its journey and when it arrived and the light would have travelled a measurable light year according to this person.

The light would indeed be a light year away from where it started, but due to the apparent contraction of the space during the intermediate period the light will have travelled less than a light year, as far as she is concerned, assuming she somehow notices the contraction.

You know on Wikipedia? Why is it that some things - often plainly factual - say [citation needed] and others don't? Is it just a question of time (just not enough time to police the whole thing) or are some things just allowed through unsubstantiated?

JimBentley wrote:You know on Wikipedia? Why is it that some things - often plainly factual - say [citation needed] and others don't? Is it just a question of time (just not enough time to police the whole thing) or are some things just allowed through unsubstantiated?

JimBentley wrote:You know on Wikipedia? Why is it that some things - often plainly factual - say [citation needed] and others don't? Is it just a question of time (just not enough time to police the whole thing) or are some things just allowed through unsubstantiated?

Different people doing different stuff. Don't expect consistency!

I know, but it just seems weird. It really just came from reading an article about a singer and there was a passage about a certain single selling "approximately 496 copies" and it made me laugh (not only for the approximation of an exact number, but also that there was no citation for it). I think the same article might have contained other excellently uncheckable gems like "after buying his first bass guitar from George Harrison..." and I suppose I just sort of got around to wondering how that whole system worked.

JimBentley wrote:You know on Wikipedia? Why is it that some things - often plainly factual - say [citation needed] and others don't? Is it just a question of time (just not enough time to police the whole thing) or are some things just allowed through unsubstantiated?

Different people doing different stuff. Don't expect consistency!

I know, but it just seems weird. It really just came from reading an article about a singer and there was a passage about a certain single selling "approximately 496 copies" and it made me laugh (not only for the approximation of an exact number, but also that there was no citation for it). I think the same article might have contained other excellently uncheckable gems like "after buying his first bass guitar from George Harrison..." and I suppose I just sort of got around to wondering how that whole system worked.

I think there is supposed to be evidence for all claims, but some stuff just sneaks in I suppose. 3,476,112 articles aren't properly cited.

This is almost not a question and it's not something I've "always" wanted to know because it's kind of a new thing but what is with the whole "woke" concept? Apparently woke is now an adjective in young people's vernacular. Now i've always been one of these people who don't care for people who complain about the advancements of language and the adoption of new phrases and the whole evolution of language but even this seems like a step too far to me. It has always seemed to me that the vast majority of the kind of linguistic changes that have taken place over the years can still always be justified and no matter how strange a departure they make from so called "normal" speech there's still been an element of consistency in terms of following rules of syntax or whatever but this just doesn't make sense to me. I think this is the one phrase that has crossed a line in terms of its acceptability. To me it seems like this is the first phrase that is hiding its acceptability behind the notion that that anyone who disagrees is some kind of square who isn't accepting of the idea that language evolves. I disagree however and think it is a huge detriment to the english language.

Mark James wrote:This is almost not a question and it's not something I've "always" wanted to know because it's kind of a new thing but what is with the whole "woke" concept? Apparently woke is now an adjective in young people's vernacular. Now i've always been one of these people who don't care for people who complain about the advancements of language and the adoption of new phrases and the whole evolution of language but even this seems like a step too far to me. It has always seemed to me that the vast majority of the kind of linguistic changes that have taken place over the years can still always be justified and no matter how strange a departure they make from so called "normal" speech there's still been an element of consistency in terms of following rules of syntax or whatever but this just doesn't make sense to me. I think this is the one phrase that has crossed a line in terms of its acceptability. To me it seems like this is the first phrase that is hiding its acceptability behind the notion that that anyone who disagrees is some kind of square who isn't accepting of the idea that language evolves. I disagree however and think it is a huge detriment to the english language.

I should put people like you in the "people you shouldn't trust" thread - people who write a whole long thing on something without saying what they're talking about. Anyway, I Googled it and found this and this. It seems pretty odd, but no more or less bullshit than other things I've come across.

Mark James wrote:This is almost not a question and it's not something I've "always" wanted to know because it's kind of a new thing but what is with the whole "woke" concept? Apparently woke is now an adjective in young people's vernacular. Now i've always been one of these people who don't care for people who complain about the advancements of language and the adoption of new phrases and the whole evolution of language but even this seems like a step too far to me. It has always seemed to me that the vast majority of the kind of linguistic changes that have taken place over the years can still always be justified and no matter how strange a departure they make from so called "normal" speech there's still been an element of consistency in terms of following rules of syntax or whatever but this just doesn't make sense to me. I think this is the one phrase that has crossed a line in terms of its acceptability. To me it seems like this is the first phrase that is hiding its acceptability behind the notion that that anyone who disagrees is some kind of square who isn't accepting of the idea that language evolves. I disagree however and think it is a huge detriment to the english language.

I should put people like you in the "people you shouldn't trust" thread - people who write a whole long thing on something without saying what they're talking about. Anyway, I Googled it and found this and this. It seems pretty odd, but no more or less bullshit than other things I've come across.

I was very drunk and immediately regretted posting this when I woke up this morning.

I've got a broad template for those articles. Just delete as applicable and insert the values and information you want:

"Unless you've been living under a rock/in a cave/on Mars/in prison for the last {insert value x} days/weeks/months/years, then you WILL have/MUST have/can't have avoided/fallen in love with {insert fleetingly insignificant internet trend here}!"

"Although this {trend} has been around in internet circles/the gay community/the black community/the trans community/neocon organisations/hard left factions for {insert value x} days/weeks/months/years, its current ubiquity can be directly traced to {insert a recent tangentially-related news story here}."

"Google/Yahoo/Twitter/Facebook users have been making claims that {fleetingly insignificant internet trend] is the best/worst thing that has ever happened, but other Google/Yahoo/Twitter/Facebook users are more cautious, warning that it might actually be a bad/good thing."

"Whatever, it looks as though {fleetingly insignificant internet trend} is here to stay!"

I've got a broad template for those articles. Just delete as applicable and insert the values and information you want:

"Unless you've been living under a rock/in a cave/on Mars/in prison for the last {insert value x} days/weeks/months/years, then you WILL have/MUST have/can't have avoided/fallen in love with {insert fleetingly insignificant internet trend here}!"

"Although this {trend} has been around in internet circles/the gay community/the black community/the trans community/neocon organisations/hard left factions for {insert value x} days/weeks/months/years, its current ubiquity can be directly traced to {insert a recent tangentially-related news story here}."

"Google/Yahoo/Twitter/Facebook users have been making claims that {fleetingly insignificant internet trend] is the best/worst thing that has ever happened, but other Google/Yahoo/Twitter/Facebook users are more cautious, warning that it might actually be a bad/good thing."

"Whatever, it looks as though {fleetingly insignificant internet trend} is here to stay!"

As well as that sort of situation (rare but significant for its historical precedence), I think it's far more to do with it being far safer for the prison personnel (or whoever carries out the injections) to be working with sterile equipment.

Plus the "lethal injection" is actually a process of injections (three of four separate drugs I think) administered in a specific order in an attempt to make the death more "humane", so any potential introduction of pathogens from an infected needle might well interfere with that process. But on the whole I reckon it's more down to wanting to keep the prison personnel safe.

As well as that sort of situation (rare but significant for its historical precedence), I think it's far more to do with it being far safer for the prison personnel (or whoever carries out the injections) to be working with sterile equipment.

Plus the "lethal injection" is actually a process of injections (three of four separate drugs I think) administered in a specific order in an attempt to make the death more "humane", so any potential introduction of pathogens from an infected needle might well interfere with that process. But on the whole I reckon it's more down to wanting to keep the prison personnel safe.

Indeed. Basically, there's no reason not to - the possibilities it guards against are all very unlikely, but possible nonetheless, so might as well.

Eoin Monaghan wrote:
He may not be liked on here, but you have to give some credit to Mark

Marc Meakin wrote:On a similar theme, why did your mum tell you not to swig germs from a cough medicine bottle....you already have germs

I'm still trying to figure out what this means, I mean, it looks like a sentence and all that but I can't get it to make sense however I look at it. Why would you be drinking cough medicine from the bottle? Why would your mum let you? And why would she think that cough medicine contains germs? All they are is combinations of mild painkillers, anti-inflammatories, possibly antitussives in a syrup suspension.

That's a bit of a strange case, but with the needles already in his arms, they could have executed him anyway just before the stay of execution came. So an equally good solution would be the carry out the execution five seconds later than you would otherwise have done.

Quite a few adverts show customer data at the bottom of the screen such as "84% of 189 women agree" and so forth. This can easily (if you're stupid or not paying attention) be misread or misinterpreted as "84 out of 189", which isn't exactly a ringing endorsement.

Why don't they restrict the sample size based on the feedback as they go along? If only about half the respondents seem to like the product then stop asking after about 54 people - "50% of 54 women agree" sounds better than "50% of 106 agree". Or would nobody be fooled?

Fred Mumford wrote:Quite a few adverts show customer data at the bottom of the screen such as "84% of 189 women agree" and so forth. This can easily (if you're stupid or not paying attention) be misread or misinterpreted as "84 out of 189", which isn't exactly a ringing endorsement.

Why don't they restrict the sample size based on the feedback as they go along? If only about half the respondents seem to like the product then stop asking after about 54 people - "50% of 54 women agree" sounds better than "50% of 106 agree". Or would nobody be fooled?

I get what you mean, but I don't think anyone would notice much difference

COUNTDOWN or THETUBE? Which is better? There's only one way to find out....

Fred Mumford wrote:Quite a few adverts show customer data at the bottom of the screen such as "84% of 189 women agree" and so forth. This can easily (if you're stupid or not paying attention) be misread or misinterpreted as "84 out of 189", which isn't exactly a ringing endorsement.

Why don't they restrict the sample size based on the feedback as they go along? If only about half the respondents seem to like the product then stop asking after about 54 people - "50% of 54 women agree" sounds better than "50% of 106 agree". Or would nobody be fooled?

At 50%, I think I'd just leave it out to be honest.

Eoin Monaghan wrote:
He may not be liked on here, but you have to give some credit to Mark

Fred Mumford wrote:Quite a few adverts show customer data at the bottom of the screen such as "84% of 189 women agree" and so forth. This can easily (if you're stupid or not paying attention) be misread or misinterpreted as "84 out of 189", which isn't exactly a ringing endorsement.

Why don't they restrict the sample size based on the feedback as they go along? If only about half the respondents seem to like the product then stop asking after about 54 people - "50% of 54 women agree" sounds better than "50% of 106 agree". Or would nobody be fooled?

Kinetic energy is 0.5mv^2. So if something going 1 m/s has 1 unit of energy, then something going 2 m/s has 4 units of energy. So if a vehicle is travelling at 1 m/s already, then it should take three times as much energy to reach 2 m/s as it did going from 0 to 1 m/s.

But speed is a relative thing isn't it? If there is a spaceship that is stationery relative to Earth, then it could have a blast on its rockets to then be going at 1 m/s relative to Earth. But what if it did the same again to go at 2 m/s relative to Earth? How much energy would that take? Three times as much? But there could be another spaceship next to it that did the first blast in unison with it. So the second blast would make the spaceship go from 0 to 1 m/s relative to this other spaceship but from 1 to 2 m/s relative to Earth.

40.5J to get your spaceship from zero to 9m/s. And yes, I know where this is going. Someone who's done physics more recently than me is welcome to explain the answer, cos I'm now confused too, something to do with the rate of acceleration probably.

Ian Volante wrote:In a nutshell, it is correct to look at the change in velocity rather than the overall velocity.

But I could increase a vehicle's velocity by 2m/s or by 1m/s twice. Is there a difference?

Not as far as I can see. To increase its velocity by 1m/s takes the same amount of energy whether it's going at 9m/s or 999m/s. Ignoring relativity anyway.

The kinetic energy needed to get an object from speed u to speed v is 1/2mv^2 - 1/2mu^2 = 1/2*m(v^2 - u^2).
If v = u + 1 (so increasing it by 1m/s), this becomes 1/2*m(2u+1) which very much depends on the initial speed.

Conor wrote:The kinetic energy needed to get an object from speed u to speed v is 1/2mv^2 - 1/2mu^2 = 1/2*m(v^2 - u^2).
If v = u + 1 (so increasing it by 1m/s), this becomes 1/2*m(2u+1) which very much depends on the initial speed.

So how much fuel will I need to use to accelerate my spaceship by 1m/s? It's currently already going 1m/s relative to Earth, but it's stationary relative to the spaceship next to it. I want it to be going at 2m/s relative to Earth and 1m/s relative to the spaceship next to it.

While do people feel the need to have two separate two-minute silences to mark the end of the First World War? And when the 11th November falls on a Sunday, they seem to invent some other day just to make sure we get two. I think it's insane.

Gavin Chipper wrote:While do people feel the need to have two separate two-minute silences to mark the end of the First World War? And when the 11th November falls on a Sunday, they seem to invent some other day just to make sure we get two. I think it's insane.

I agree. The addition of another minute of silence this year - ostensibly to mark a train crash - is particularly egregious. I'm pretty sure that everyone affected by that particular crash has already mourned in their own way; it was awful, of course, but to put it alongside the millions who died in World War 1 is frankly ridiculous.

Gavin Chipper wrote:While do people feel the need to have two separate two-minute silences to mark the end of the First World War? And when the 11th November falls on a Sunday, they seem to invent some other day just to make sure we get two. I think it's insane.

I agree. The addition of another minute of silence this year - ostensibly to mark a train crash - is particularly egregious. I'm pretty sure that everyone affected by that particular crash has already mourned in their own way; it was awful, of course, but to put it alongside the millions who died in World War 1 is frankly ridiculous.

There's an ongoing thread here in the office on a similar sentiment - we just had a minute's silence for a year-old event in Paris while ignoring all of the equally worthy deaths of numerous people in other bits of the world. Gobshitery at its worst. In protest, I loudly stomped through the office to make a cup of tea.

Gavin Chipper wrote:While do people feel the need to have two separate two-minute silences to mark the end of the First World War? And when the 11th November falls on a Sunday, they seem to invent some other day just to make sure we get two. I think it's insane.

I agree. The addition of another minute of silence this year - ostensibly to mark a train crash - is particularly egregious. I'm pretty sure that everyone affected by that particular crash has already mourned in their own way; it was awful, of course, but to put it alongside the millions who died in World War 1 is frankly ridiculous.

There's an ongoing thread here in the office on a similar sentiment - we just had a minute's silence for a year-old event in Paris while ignoring all of the equally worthy deaths of numerous people in other bits of the world. Gobshitery at its worst. In protest, I loudly stomped through the office to make a cup of tea.

I think there's a certain amount of "being seen to be altruistic" going on with people lately; it's completely misguided (in my opinion) but I'm sure it makes them feel as though they're good and are doing good things.

Actually I might have to make a new topic about this whole phenomenon, as it ties into another weird modern thing, which is the taking up of causes in the news by people who are entirely unaffected by said causes (I'm thinking in particular of the UK "Black Lives Matter" protests; whilst it's definitely an issue in America, I don't believe that there's a comparable situation in the UK and as such, the protests probably did more harm than they did good).

By the way, I generally don't do silences at all. Any of them. I don't have a problem with people doing them, but I think they should be a personal thing. There are many ways people can remember or show respect, and having large public mass silences strikes me as a bit of an illiberal way of doing things, because people in the vicinity feel compelled to join in. It needs to be a voluntary thing or it defeats the point.